The proposed study is a continuation of a longitudinal investigation of bone mineral loss and nonviolent fractures started in 1981 on a homogeneous population of 2,500 Japanese-American men and women on the island of Oahu. Further data points will be obtained in order to determine accurate bone loss rates in the distal radius, proximal radius, and os calcis by photon absorpitometry. Serial measurements of spinal bone mineral with dual photon absorptiometry will also be initiated. An additional 100 premenopausal women in the age range 30-50 will also be recruited. Bone mineral content (BMC) and loss rates will be correlated with fractures, diet, physical activity, reproductive variables, estrogen use, and diseases potentially contributing to bone loss. A major aim of the study is to define "high risk" individuals. The definition of the "high risk" individual will depend primarily upon rates of appendicular or axial bone loss. However, various prediction and normalization techniques will also be tested for their ability to characterize the "high risk" individual. In addition, 300 postmenopausal women will be stratified according to bone loss rates, and used to test the TC-99m-hydroxyethylene diphosphonate whole body retention technique for its ability to noninvasively measure bone turnover rates and predict risk. The dual photon technique will also be applied in vitro to approximately 100 lumbar spines obtained from cohort subjects at autopsy. The in vitro BMC of the spine will be compared to spinal and appendicular BMC values obtained during life, along with in vivo, high resolution radiographs and measurements of vertebral body compressive strength, in order to better define a BMC "fracture threshold." A final aim of the study is to develop well-characterized subgroups of the population for a possible, subsequent intervention trial. the subgroups will also be matched with regard to race, age, sex, body size, diet, and physical activity.